Hezbollah has launched an attack on Israeli military positions and drawn heavy return fire in the first cross-border clash for years between the longstanding foes.

Israel’s military said “two or three anti-tank missiles” had been fired from southern Lebanon toward an army base and a military ambulance but had caused no deaths or injuries..

Lt Col Jonathan Conricus, an army spokesman, also said Israel had fired back with approximately 100 artillery shells and that attack helicopters had also struck the area. The exchange “was most likely over”, he said.

Hezbollah, the pro-Iran Lebanese militant group, claimed the attack. It said its fighters had destroyed an Israeli army vehicle near the frontier in the same area. It said it had killed and wounded people inside, contradicting Israeli claims.

It was not immediately clear if there had been casualties on the Lebanese side.

Hezbollah’s deputy leader had said his forces would launch a surprise retaliatory strike against Israel. “I rule out that the atmosphere is one of war – it is one of a response to an attack,” Sheikh Naim Qassem said in a TV interview on Tuesday night. “Everything will be decided at its time.”

Israel has not claimed the Beirut strikes, but two western diplomats said the rare operation may have been an assassination attempt or an effort to destroy equipment for fitting advanced guidance systems to rudimentary rockets.

Israel also said last week it had intelligence that Iran was helping Hezbollah to build guided missiles in Lebanon, something it said it would not tolerate. Guided missiles rather than the imprecise rockets it has used in the past would allow Hezbollah to target vital Israeli infrastructure in any future conflict.

Neither Israel nor Hezbollah has expressed an interest in a return to war, having fought a deadly month-long conflict in 2006 that killed about 1,200 people in Lebanon, mostly civilians, and roughly 160 in Israel.

They have largely refrained from direct fighting for the past 13 years, save a few isolated flareups. Hezbollah fired an anti-tank missile in 2015 that killed two Israeli soldiers. Israel responded by shelling the area, killing a UN peacekeeping soldier.

However, tensions between Israel and Iran, Hezbollah’s founder and patron, have peaked recently and threatened to drag Lebanon and Israel into renewed conflict.

The Israeli air force has bombed Iranian military assets in Syria, saying its arch-enemy is using the country as a base to attack it.

It has also been accused of bombing Hezbollah forces operating in Syria, where the group is allied with the country’s president, Bashar al-Assad. Until last week, Israel appeared to have avoided striking Hezbollah on home soil in Lebanon, fearing it may lead to reprisal attacks.

Following Sunday’s violence, Israel’s president, Reuven Rivlin, said the country was “ready and willing to defend Israel’s citizens wherever they are, without hesitation. We are prepared and do not want to show just how well-prepared we are.”